a) Field of the Invention
The present invention relates to an apparatus and method for display signs where the image or message can be easily and rapidly displayed, and readily changed to some other image or message. More particularly, the present invention relates to such a display sign which is capable of providing multiple color displays.
b) Background Art
For many decades, there have been various matrix display signs made up of display elements, pixels or the like which are selectively activated to display a picture or a message. In its simplest form, such a display sign comprises an array of incandescent lamps, each of which can selectively be turned on or off. However, as these signs become quite large, the expense and the practical problems increase substantially.
If the sign is as large as 4.times.8 feet, or even 10.times.20 feet, the individual picture elements (or pixels) can be arranged in as many as several hundred to a thousand or more columns and possibly as many rows. Then there are considerations of providing a practical control and actuating system which is sufficiently versatile to meet the practical requirements of operating effectively to display different pictures or messages. Further, there are considerations of reliability, and the level of maintenance required.
Then there are the considerations which might be termed the "aesthetics" of the display sign. Desirably the individual elements are so arranged that the character of the picture has precision and is visually attractive. Normally, this would require that the individual picture elements are positioned so as to minimize any "gaps" (spaces between the illuminating portions of the display elements).
One of the more significant challenges has been to provide display signs which are multi-colored. The technology of colored TV is, as a practical matter, not readily adapted to a very large display sign.
A search of the patent literature has disclosed a number of U.S. patents relating to display signs in general. These are as follows:
U.S. Pat. No. 2,154,110 (Parks) discloses an illuminated type display device for billboard advertising, etc. There is a plurality of light tubes 13 positioned parallel and closely adjacent to one another, and arranged to be in the same plane. These are arranged in three groups each, with the tubes in each group of three having a different gas therein or otherwise arranged, so that these adjacent tubes in each group are green, red and blue. There are possibly two hundred to nine hundred such tubes.
There is a plurality of solenoid operated flexible resilient plates positioned along the length of each tube, as shown in FIGS. 7 and 8. In FIG. 7, the resilient plate is a resilient strip which wraps 180.degree. around one portion of one tube. The strip is attached to a solenoid which is spring loaded to its out position where the element would be covering the light. When the solenoid is activated against the urging of the spring, the masking element is withdrawn, as shown in the lower part of FIG. 7, to let that portion of the tube shine through. Thus, by selectively operating various solenoids, different pixels will show up, some red, some green, and some blue, to form a composite picture.
The solenoids are controlled from a switch board, where there are a plurality of switch elements, some of which are connected to raised portions of a conducting plate, which is in turn connected to a battery. The raised portions are in contact with selected switches, and the recessed portions are out of contact. This middle conducting board is made by an etching process. The plate has a sensitized plate or film placed thereon, and this in turn is covered by a color filter which has a plurality of colored strips, and arranged in the same red, green and blue pattern as the tubes which are illuminated. The picture or graphics to be represented on the sign is photographed as a negative against the screen, and thus the image to be photographed appears on the sensitized film, where certain unexposed areas correspond to locations of the red, green and blue locations. Then the plate is put to an etching process to create the recess. To display the picture, the plate is then placed against the switch board, as shown in FIG. 1, thus making contact with the appropriate switches, which in turn retract the masking elements.
Another arrangement of the solenoid is shown in FIG. 9, where the masking member has a hinge element. Yet another arrangement is shown in FIG. 10 where the masking strip extends from a spring around a U shaped housing at a portion of the light tube, with the other end of the masking member connecting to a solenoid element.
Another method of creating this display is shown in FIGS. 13 and 14. This has the same sort of masking elements, which are solenoid operated, but the control board is composed of a plurality of photoelectric cells, one for each mask. The image is projected by a projector against the control board and thus, the image projected against the photoelectric cells to activate the appropriate solenoids to withdraw the related masks to form the image.
U.S. Pat. No. 5,132,675 (Dabbaj) discloses a system for display signs where there are individual pixel elements. Each pixel element has a set of different colored vanes which appear to be in the form of flat plates which are moved outwardly by electromagnetic means to different locations displaying different colored areas across the vanes to get different color mixes. Six distinct mixes can be obtained by using three vanes per set.
U.S. Pat. No. 3,250,031 (Bowman) shows a display unit for score boards where there are a plurality of window sets, each displaying a number. As can be seen in FIG. 1, there is an array of approximately twenty window segments, each having a retractable display portion which can be retracted by a solenoid. By placing the appropriate display elements together, all of the ten numerals can be displayed.
U.S. Pat. No. 640,153 (Yaxley) shows a solenoid that moves an optical element in a signaling device.